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SubjectRe: [PATCH] net: add ability to clear stats via ethtool - e1000/pcnet32
On Sun, 1 Jun 2008, Ben Hutchings wrote:

> Bill Fink wrote:
> <snip>
> > Yes, every individual Linux network administrator can re-create the
> > wheel by devising their own scripts, but it makes much more sense
> > to me to implement a simple general kernel mechanism once that could
> > be used generically, than to have hundreds (or thousands) of Linux
> > network administrators each having to do it themselves (perhaps
> > multiple times if they have a variety of types of systems and types
> > of NICs).
> The ethtool interface is pretty generic, even if the names aren't.
> Here's some Python code I just knocked up which demonstrates how
> to get a set of named stats. It shouldn't be terribly hard to
> extend this to saving and subtracting stat sets.

I'm not sure what that proves. Your python code just basically gives
the same info as running the "ethtool -S" command. But the question
is how does one devise a generic script or tool that doesn't require
any special knowledge of the specific NIC being used. For example,
here's the "ethtool -S" info for my myri10ge NIC:

[root@chance8 ~]# ethtool -S eth2
NIC statistics:
rx_packets: 53243864310
tx_packets: 112826823797
rx_bytes: 301727733072710
tx_bytes: 716648208451198
rx_errors: 0
tx_errors: 0
rx_dropped: 0
tx_dropped: 0
multicast: 0
collisions: 0
rx_length_errors: 0
rx_over_errors: 0
rx_crc_errors: 0
rx_frame_errors: 0
rx_fifo_errors: 0
rx_missed_errors: 0
tx_aborted_errors: 0
tx_carrier_errors: 0
tx_fifo_errors: 0
tx_heartbeat_errors: 0
tx_window_errors: 0
tx_boundary: 4096
WC: 1
irq: 8413
MSI: 1
read_dma_bw_MBs: 1398
write_dma_bw_MBs: 1613
read_write_dma_bw_MBs: 2711
serial_number: 287046
tx_pkt_start: 1157674101
tx_pkt_done: 1157674101
tx_req: 188226127
tx_done: 188226127
rx_small_cnt: 3009560676
rx_big_cnt: 1726230729
wake_queue: 57969440
stop_queue: 57969440
watchdog_resets: 0
tx_linearized: 0
link_changes: 8
link_up: 1
dropped_link_overflow: 0
dropped_link_error_or_filtered: 26584
dropped_multicast_filtered: 2190912
dropped_runt: 0
dropped_overrun: 0
dropped_no_small_buffer: 0
dropped_no_big_buffer: 0

How does one know which of these reported values are counter stats
that one wishes to zero/snapshot, and which are not?

Another issue that occurred to me is if multiple people are working
on troubleshooting a network problem, how do we insure that they all
get a consistent view of the stats? If this is done via a kernel
mechanism then there isn't an issue. But if it's done via user space,
then you have to make sure that everyone zeros/snapshots the stats
at the same time.

Ideally, one should be able to do something like "ethtool -z ethX"
to zero/snapshot the driver stats, and then "ethtool -S ethX" to get
the stats since the last snapshot. You should be able to use the
same tool ("ethtool") to do all of this, and not some other special
tool or specially devised homegrown script. Why make users lives
any more difficult than need be?


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